1. Field of the Invention
This invention relates to utility ladders having various modes of usage.
2. Brief Description of the Prior Art
A number of types of utility ladders have previously been proposed, and several of these have been patented. The following prior art known to Applicant is related to the subject matter of the present invention.
Richards U.S. Pat. No. 2,350,129 discloses a ladder composed of multiple parts which can be used as an extension ladder or can be easily converted into a step ladder. The extension ladder is to some extent limited in the adjustability of its length to certain fixed increments.
Cormier U.S. Pat. No. 3,476,211 discloses another type of ladder which can be used either as an extension ladder or as a step ladder.
Couse U.S. Pat. No. 2,834,528 discloses a convertible ladder which can be utilized as an extension ladder or as a step ladder. The Couse convertible ladder includes a pair of curved elements which are inserted in side rails of one of the ladder sections and can be used to hook over a horizontally projecting ledge to help maintain the position of the ladder against the side of a building.
Morris U.S. Pat. No. 1,987,535 discloses a folding extensible ladder which can be folded into a flat status for transport and storage, or can be folded to an angulated position and used as a step ladder. When the ladder is folded to another position, it can be used as an extension ladder.
Another type of utility ladder which is similar in some respects to the present invention is that which is illustrated and described in Hughes U.S. Pat. No. 4,060,150. The Hughes patent discloses a ladder which can be extended in its length by joining several sections to each other in an interfitting telescoping relationship, and which can be provided with a bridging or pedestal element for joining several sections to each other to form a step ladder structure. The rails of one of the ladder sections can also be connected to hook-like appendages which will permit a section of the ladder carrying such appendages to be hooked over a horizontal pole or branch with the ladder section suspended from the hook elements.
Another type of utility ladder having telescoping ladder sections which can be joined by a pedestal element to form a step ladder arrangement is that which is depicted and described in Leavitt et al U.S. Pat. No. 2,900,041.